Impact energy
Impact energy is the energy of motion an asteroid or meteoroid carries, released when it hits a planet or its atmosphere.
Impact energy is the kinetic energy of an object, its energy of motion. It equals half its mass multiplied by the square of its speed. Because speed is squared, doubling the speed quadruples the energy. That is why even small space rocks are so powerful: they travel tens of kilometres every second.
When an asteroid hits the ground, its energy is turned into heat, shock waves and the motion of rock thrown out of the crater. A metre-sized stony meteoroid releases energy roughly equal to a few tens of tonnes of TNT, mostly high in the atmosphere. A 50-metre iron asteroid, like the one that made Meteor Crater in Arizona about 50,000 years ago, released something like 10 megatonnes.
Scientists estimate impact energies from fireball brightness, infrasound and crater size. These numbers help assess the risk from asteroids of different sizes and decide how much effort to put into finding them.
Related terms
Level: Explorer Ages 10 and up